In radio communication systems such as mobile phone systems, radio base stations (evolved Node B (eNB)) communicate with mobile terminals (user equipment (UE)) located in cells covered by the radio base stations. Each radio base station is assigned a unique cell identifier that is different from the cell identifier of an adjacent or nearby radio base station so that the mobile terminals can identify the cell covered by the radio base station. For example, when a first radio base station is assigned a first cell identifier, a second radio base station that is adjacent or near the first radio base station is assigned a second cell identifier that is different from the first cell identifier. Alternatively, when a first radio base station is assigned a first cell identifier, a second radio base station that does not have a cell overlapping a cell covered by the first radio base station (i.e., that is distant from the first radio base station) may be assigned the first cell identifier or may be assigned a second cell identifier that is different from the first cell identifier. Thus, each mobile terminal uses the cell identifier to identify the radio base station with which it is to communicate and transmits/receives data to/from the identified radio base station.
Examples of related art include Japanese Unexamined Patent Application Publication No. 11-64014.
An operator who installs or maintains the radio base stations manually assigns the cell identifiers to the radio base stations so that the same cell identifier is not redundantly assigned to adjacent or nearby ones of the radio base stations, that is, so that the cell identifiers do not conflict with each other between adjacent or nearby ones of the radio base stations. More specifically, the operator manually assigns the cell identifiers to the radio base stations, considering various factors, such as the locations where the radio base stations are installed, cell coverages (or cell radii) covered by the radio base stations, the presence/absence of obstacles to radio waves emitted from the radio base stations, and results of actual field evaluation. Thus, costs (e.g., temporal cost, expense cost, and operational cost) for assigning the cell identifiers to the radio base stations increase significantly.